Ensuring working conditions along a longwall face

ABSTRACT

A longwall installation unit is disclosed. The longwall installation unit may form a longwall installation assembly together with other longwall installation units of the same kind. The longwall installation assembly may extend along the longwall face in a longwall mine. The longwall mine may have a compressor device. The longwall installation unit may have a dilution gas nozzle configured to be fluidly connected to the compressor device.

TECHNICAL FIELD

The present disclosure relates to a method and device for ensuringworking conditions, and more particularly to a method and device forensuring working conditions along a longwall face in an undergroundmine.

BACKGROUND

A known problem in longwall mining of coal seams is gas emission ofmethane gas. That methane gas emission results from both natural outflowand generation during the coal winning process. Capillary bound methanegas is released from the coal as the extraction machine cuts along thecoal seam. That released methane gas bears the risk of methane gasexplosions.

Generally, ventilation of the mine allows maintaining gas concentrationsat an acceptable level. For example, ventilation provides air from anair inlet side, guides the same along the longwall, and releases thesame at an outlet side, thereby taking with it any released methane gas.

Nevertheless safety regulations require measuring the methane gasconcentration constantly in underground mining. If a measured methanegas concentration reaches a critical value, the entire longwall mineincluding, for example, extraction machine, shield supports and haulagesystems is stopped until the methane gas concentration undercuts astatutory level. Those stops and even more the following boot-upprocedure of the longwall mine are responsible for a majority ofoperation stops and failures in winning processes having increasedmethane gas emissions as it is typically the case in longwall mining ofthin coal seams.

For a longwall mine, DE 10 2007 014 662 A1 discloses a gas measurementarrangement with a plurality of gas sensors. In case a calculatedextraction rate of the extraction machine does not correlate with ameasured gas concentration, a warning signal is provided.

The present disclosure is directed, at least in part, to improving orovercoming one or more aspects of prior systems.

SUMMARY OF THE DISCLOSURE

According to a first aspect of the present disclosure, a longwallinstallation unit configured to form a longwall installation assemblytogether with a plurality of longwall installation units of the samekind to extend along the longwall face in a longwall mine having acompressor device is disclosed. The longwall installation unit maycomprise a dilution gas nozzle installed in the longwall installationunit and configured to be fluidly connected to the compressor device.

According to another aspect of the present disclosure, a method forensuring working conditions along a longwall face in an underground minecomprises providing a mine ventilation, and in addition to the mineventilation, providing a dilution gas to the longwall face from at leastone of a plurality of dilution gas supply units arranged at spatiallyseparated positions along the longwall face.

Other features and aspects of this disclosure will be apparent from thefollowing description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of an exemplary longwall mine; and

FIG. 2 is a schematic drawing of an exemplary shield support and anexemplary face conveyor segment.

DETAILED DESCRIPTION

The following is a detailed description of exemplary embodiments of thepresent disclosure. The exemplary embodiments described therein andillustrated in the drawings are intended to teach the principles of thepresent disclosure, enabling those of ordinary skill in the art toimplement and use the present disclosure in many different environmentsand for many different applications. Therefore, the exemplaryembodiments are not intended to be, and should not be considered as, alimiting description of the scope of patent protection. Rather, thescope of patent protection shall be defined by the appended claims.

The present disclosure is based in part on the realization thatconventional ventilation systems in longwall mining may be notsufficient to dilute released methane gas, and direct the same away fromthe longwall face. For example, if mining thin coal seams, small crosssection areas limit ventilation flows as working conditions for man andmachine decrease if ventilation is increased. This may in particular bethe case if local methane gas concentrations are temporarily and locallyincreased.

Longwall installation units as disclosed herein may be capable tospecifically provide dilution gas to desired regions of the longwallface, thereby specifically diluting measured methane gas concentrationpeaks and ensuring acceptable working conditions for man and machine.

An exemplary longwall mine 1 is shown in FIG. 1. For the purpose ofmining coal along a longwall face 2, longwall mine 1 comprises a faceconveyor 4 with a main drive 6 and an auxiliary drive 8, and anextraction machine 10 carried by face conveyor 4.

In operation, extraction machine 10 cuts along longwall face 2 in areciprocating manner to extract coal 3. For example, extraction machine10 may be a shearer or a plow. Material mined by extraction machine 10drops onto face conveyor 4 that transports the extracted pieces of rockand minerals to a main roadway 12 (also referred to as drift). There,the extracted pieces are passed to a pass-over conveyor or roadwayconveyor 14. The transported pieces may be crushed and furthertransported via, for example, a belt conveyor.

Face conveyor 4 is arranged along longwall face 2 and comprises aplurality of face conveyor segments 5. Neighboring face conveyorsegments 5 are connected to one another, for example, so as to resistseparation when a tensile force is applied and so as to restrictrelative angular movement. For example, face conveyor segments 5 arearranged in a row between two stations, which respectively accommodatesprockets and use the sprockets to redirect a conveyor chain of faceconveyor 4.

To maintain longwall face 2 accessible, a shield support assembly 17 isarranged along longwall face 2. Shield support assembly 17 comprises aplurality of shield supports 16 arranged along longwall face 2. At eachshield support 16, a moving device (not shown) is supported, which canconsist of in each case one pushing or walking bar, which can be loadedhydraulically in both directions in order to push face conveyor 4optionally and section by section in the work direction (arrow A) orpull up individual shield supports 16 in the work direction. Longwallface 2 is further kept open by shield caps forming an upper unit of eachshield support 16. Surrounding rock can only break in and form theso-called old workings after advancing of shield supports 16.

Longwall mine 1 is equipped with a plurality of dilution gas supplyunits 20 connected via control connection line 22 (indicated by a dasheddotted line in FIG. 1) to a control unit 24, and connected via apressurised dilution gas line 26 (indicated by a solid line in FIG. 1)to a dilution gas source 27.

Each dilution gas supply unit 20 comprises a dilution gas nozzle 30. Adilution gas valve 28 may be fluidly interconnected between dilution gassource 27 and dilution gas nozzle 30. Each dilution gas valve may beassociated with dilution gas supply unit 20 or may be installed withindilution gas line 26. As exemplarily shown in FIG. 1, dilution gasnozzles 30 are installed regularly at every third shield support 16.Dilution gas nozzles 30 are, thus, spatially separated at variouspositions along longwall face 2. Dilution gas nozzle 30 may be oriented,for example facing longwall face 2, such that dilution gas can bereleased toward longwall face 2 if dilution gas valve 28 is opened and,thus, allows flow of dilution gas out of a respective gas nozzle 30.

Dilution gas valve 28 is, for example, a shut-off valve configured toeither allow or block flow of dilution gas from dilution gas line 26 todilution gas nozzle 30. Alternatively, dilution gas valve 28 may be acontrol valve configured to control the amount of said dilution gas flowthere through.

Control unit 24 provides signals causing dilution gas valve 28 to adoptits state via control connection line 22. Control unit 24 may be asingle microprocessor or plural microprocessors that may includes meansfor controlling, among others, an operation of the various components oflongwall mine 1. Control unit 24 may include all the components requiredto run an application such as, for example, a memory, a secondarystorage device, and a processor such as a central processing unit or anyother means known in the art for controlling longwall mine 1 and itsvarious components. Various other known circuits may be associated withcontrol unit 24, including power supply circuitry, signal-conditioningcircuitry, communication circuitry, and other appropriate circuitry.Control unit 24 may analyze and compare received and stored data, and,based on instructions and data stored in memory or input by a user,determine whether action is required. For example, control unit 24 maycompare received values with target values or preset threshold valuesand trends stored in memory, and based on the results of the comparison,control unit 24 may transmit signals to one or more components to alterthe operation status thereof.

Control unit 24 may include any memory device known in the art forstoring data relating to operation of longwall mine 1 and itscomponents. The data may be stored in the form of one or more maps thatdescribe and/or relate, for example, valve opening timing. Each of themaps may be in the form of tables, graphs, and/or equations, and includea compilation of data collected from lab and/or field operation oflongwall mine 1. The maps may be generated by performing instrumentedtests on the operation of longwall mine 1 under various operatingconditions while varying parameters associated therewith. Control unit24 may reference these maps and control operation of one component inresponse to the desired operation of another component.

As used herein, the term “connected” used in connection with the controlunit refers to the presence of a control connection line and the abilityof the control unit to control operation of a connected component,and/or receive control signals or measured values from a connectedcomponent.

Dilution gas source 27 may be arranged at any place of the undergroundmine and/or the surface and may be connected to control unit 24.Usually, dilution gas source 27 is substantially free of methane gas. Toprovide a dilution gas to dilution gas line 26 with a pressure aboveambient pressure, dilution gas source 27 may be, for example, acompressor device. Dilution gas source 27 may provide air drawn from thesurface and/or well-ventilated regions of the underground mine such asroadway 12.

In the shown configuration of FIG. 1, every third shield support 16 isequipped with a dilution gas nozzle 30 such that dilution gas nozzles 30are arranged spaced from one another along longwall face 2. In otherembodiments, the distance between neighboring dilution gas nozzles 30may be lower or greater depending on various influences including, butnot limited to, size of shield support 16, strength of ventilation(indicated by arrow V), height of coal seam 3. For example, dilution gasnozzles 30 may be arranged every 10 to 30 meters along longwall face 2.

The present disclosure is not limited to embodiments, in which solelyshield supports 16 are equipped with dilution gas nozzles 30. Generally,any longwall installation unit, such as face conveyor segments 5 orshield supports 16, configured to form a longwall installation assembly,such as face conveyor 4 or shield support assembly 17, together with aplurality of longwall installation units 5, 16 of the same kind toextend along longwall face 2 in a longwall mine 1 may comprise dilutiongas nozzle 30. Dilution gas nozzle 30 may be installed in longwallinstallation unit 5, 16 and configured to be fluidly connected tocompressor device 27. It is noted that dilution gas supply relatedfeatures described in connection with shield support 16 or face conveyorsegment 5 may be also applicable to other longwall installation units.Face conveyor segment 5 and shield support 16 are only exemplaryembodiments of longwall installation units.

In some embodiments, each longwall installation unit 5, 16 may compriseone or more respective dilution gas nozzles 30, in other embodimentsevery second to every fifteenth longwall installation unit 5, 16 maycomprise one or more dilution gas nozzles 30. In other words, of theplurality of longwall installation units 5, 16, at least a sub-group ofthe plurality longwall installation units 5, 16 may have a dilution gasnozzle 30.

Although shown in FIG. 1, dilution gas nozzles 30 may not necessarily bearranged equidistantly. For example, a distance between neighboringdilution gas nozzles 30 may decrement towards a centre region oflongwall face 2, or may decrement in direction of mine ventilation (V).

Referring again to FIG. 1, distributed along longwall face 2, methanegas sensors 32 are installed in longwall mine 1. In the shownconfiguration, some of shield supports 16 are equipped with methane gassensors 32 being configured to measure a methane gas concentration atspatially separated regions. Alternatively, at least some of faceconveyor segments 5 may be equipped with methane gas sensors 32.

As each methane gas sensor 32 is connected via control connection line22 to control unit 24, signals indicating a methane gas concentration ata respective methane gas sensor 32 can be provided to control unit 24 inform of signals. For example, methane gas sensors 32 may be arrangedalong longwall face 2 such that neighboring methane gas sensors 32 arespaced from one another within a range from 5 m to 50 m, such as withina range from 10 m to 30 m.

Each methane gas sensor 32 may have a minimum distance to a neighboringdilution gas nozzle 30. Said minimum distance may be set to ensure thata methane gas sensor does not directly come into contact with dilutiongas at the moment in which the same is supplied by respective dilutiongas supply unit 20 such that measurements of methane gas sensors 32 maybe not falsified as those would not longer be representative for therespective region. A minimum distance as used herein refers to acombination of distances along each spatial axis, which at least ensuresa reduction of the effect of a “short-circuit” between a dilution gasnozzle and a methane gas sensor. For example, a minimum distance indirection of longwall face 2 between neighboring methane gas sensor 32and dilution gas nozzle 30 may be at least 1 m, and/or a distancebetween a methane gas sensor 32 and longwall face 2 in direction ofworking direction A may be greater than a distance between a neighboringdilution gas nozzle 30 and longwall face 2 in direction of workingdirection A.

A user input device 34 and a display device 36 are arranged, forexample, in a displaceable manner, at an accessible location of longwallmine 1. User input device 34 and display device 36 are connected viarespective connection lines 38, 40 to control unit 24.

Using user input device 34 and optionally display device 36, a miner cancontrol operation of longwall mine 1 including, but not limited to,cutting depth, cutting speed, advancing speed, conveyor speed, and/ordilution gas supply. To enable user inputs, user input device 34 isconfigured to receive the same, for example, via a keyboard or a touchpanel. Display device 36 is configured to visualize information receivedfrom control unit 24.

A ventilation system of the mine provides air through roadways 12 andalong longwall face 2 as indicated by direction arrows V. Theventilation system may be set up such the mine ventilation can beadapted generally by control unit 24.

FIG. 2 shows an exemplary embodiment of shield support 16 to hold openlongwall face 2 and a face conveyor segment 5.

Shield support 16 comprises skids 42, hydraulic cylinders 44, a shieldcap 46, and a gob shield 50 and is equipped with a dilution gas nozzle30.

Shield support 16 has two mutually adjacent skids 42, which inunderground mining are also referred to as floor skids, since they reston the rock soil forming the floor of a face. On each floor skid 42, amultitelescopic strong hydraulic cylinder 44 (in underground mining alsoreferred to as a hydraulic prop) is supported. The cylinder head ofhydraulic cylinder 44 presses from below against a shield cap 46. Shieldcap 46, which is in underground mining also referred to as a roof cap,presses against the rock which forms the ceiling of the face, theso-called roof.

The distance between floor skids 42 and shield cap 46 can be adjusted byretraction or extension of hydraulic cylinders 44. A link mechanism 48ensures by means of a gob shield 50, as well as by means of a cornercylinder 52, that floor skids 42 and shield cap 46, in each state ofextension of hydraulic cylinders 44, stand substantially plane-parallelto each other. Link mechanism 48 is exemplary configured as a lemniscatelink mechanism. Link mechanism 48 has a front link 54 and a rear link56, both being supported at a distance apart against two boltreceptacles 58 and 60 as well as against floor skid 42.

Bolt receptacles 58, 60 are respectively configured on a side plate 62of gob shield 50, and shield cap 46 is connected to gob shield 50 in anarticulated manner by a hinge bolt. Corner cylinder 52, which isattached by its one end to a supporting bracket on gob shield 50 andwith its other end against shield cap 46, serves for the additionalbracing of the articulated connection between gob shield 50 and shieldcap 46 and can be hydraulically loaded or unloaded as desired.Additionally, a shield canopy 64 may be connected to shield cap 46 in anarticulated manner.

As mentioned above, dilution gas nozzle 30 may be installed in shieldsupport 16. In the configuration of FIG. 2, dilution gas nozzle 30 ismounted to shield canopy 64, in particular, below shield canopy 64.Alternatively, dilution gas supply unit 20 may have a differentinstallation location on shield support 16. For example, dilution gasnozzle 30 may be integrated into shield canopy 64, or may be mounted toor integrated into shield cap 46.

In the configuration shown in FIG. 2, also face conveyor segment 5 offace conveyor 4 comprises a dilution gas nozzle 30′. Said dilution gasnozzle 30′ is installed in a spill plate 66. Spill plate 66 is arrangedat a goaf side of face conveyor segment 5. Spill plate 66 may be formedby a plurality of parts or may formed as one piece. In dependence of acoal seam height, height of spill plate 66 may be chosen. A plurality ofspill plates 66 may be mounted along face conveyor 4 such thatneighboring spill plates 66 are connected to one another. For example, aspill plate may have a width, which is substantially equal to a width ofa face conveyor segment 5 along longwall face 2.

Face conveyor segment 5 may further comprise a material transport strand68 and a return travel strand 70. In the shown configuration, thematerial transport strand 68 is arranged above the return travel strand70. Both strands 68, 70 are configured to guide an endless conveyor withtransport carriers (not shown). In other embodiments, both strands 68,70 may be arranged side by side.

In some embodiments, dilution gas nozzle 30′ may be mounted at orintegrated into spill plate 66, for example, mounted at or integratedinto a top section of spill plate 66.

As already described in connection with FIG. 1, extraction machine 10 isguided at face conveyor 4.

In some embodiments, dilution gas nozzle 30, 30′ may comprise a mountingmechanism that is configured for retrofitting dilution gas nozzle 30,30′ to shield support 16 and/or face conveyor segment 5. Existing shieldsupports and/or face conveyor segments can be equipped with dilution gasnozzle 30, 30′. It will be appreciated by those having skill in the artthat exemplary disclosed shield support 16 is of a specific type asdescribed above, however, any known shield support type may be equippedwith dilution gas supply nozzle 30.

Dilution gas nozzle 30, 30′ may be installed at shield support 16 and/orface conveyor segment 5 in an adjustable manner facilitating adjustmentof the direction in which a nozzle outlet of dilution gas nozzle 30 isdirected. For example, dilution gas nozzle 30, 30′ may be pivotallyinstalled at shield support 16 and/or face conveyor segment 5.

Although not shown in FIG. 2, shield support 16 and/or face conveyorsegment 5 may be further equipped with a methane gas sensor (referred toas 32 in FIG. 1). For example, dilution gas nozzle 30 and methane gassensor 32 may be arranged side by side at shield canopy 64 ataforementioned minimum distance apart.

In some embodiments, support 16 and/or face conveyor segment 5 mayfurther comprise a dilution gas valve 28 (not shown in FIG. 2) asdescribed in connection with FIG. 1.

In some embodiments, a dilution gas line 26 (not shown in FIG. 2) may beguided below shield cap 46, for example, below a rear section of shieldcap 46, or at face conveyor 4.

INDUSTRIAL APPLICABILITY

In the following, functionality of dilution gas supply units isdescribed.

During the extraction process, longwall face 2 moves in direction ofarrow A (also referred to as working direction and advancing direction)as well as particular components of longwall mine 1 such as shieldsupports 16, face conveyor 4, and extraction machine 10 work its wayinto the seam in direction of arrow A.

As coal 3 is extracted from longwall face 2 by extraction machine 10,capillary-bound methane gas may be released from coal 3. However, notonly the extraction process itself generates methane gas, but methanegas is also released due to natural outflow.

To dilute methane gas along longwall face 2, mine ventilation (alongarrows V in FIG. 1) is provided. In addition to providing mineventilation, dilution gas can be provided to longwall face 2 from atleast one of a plurality of dilution gas nozzles 30 arranged atspatially separated positions along longwall face 2. For example,control unit 24 may cause compressor device 27 to pressurize a dilutiongas such as air, which than can be provided via dilution gas nozzles 30.It is noted that for providing dilution gas from dilution gas supplyunits 20 not necessarily measurements of methane gas concentrations needto be carried out.

Control unit 24 may further receive signals from methane gas sensors 32measuring a methane gas concentration at a plurality of spatiallyseparated regions along longwall face 2 around respective methane gassensors 32. Control unit 24 may determine a methane gas concentrationvalue for each region, and may determine at least one region for whichthe methane gas concentration value is greater than a preset thresholdvalue. In addition to mine ventilation, dilution gas from at least oneof the plurality of dilution gas nozzles 30 may be provided to thoseregions for which the methane gas concentration value is greater thanthe preset threshold value.

For example, methane gas sensor 32 measures a methane gas concentrationthat is greater than a preset threshold value and provides a respectivesignal to control unit 24. Control unit 24 than identifies at least onedilution gas supply unit 20 neighboring the respective methane gassensor 32. Then, that/those dilution gas supply units 20 determined bycontrol unit 24 is/are caused to provide dilution gas via dilution gassupply nozzle 30. To facilitate flow of dilution gas, control unit 24may provide a control signal to the respective dilution gas valve(s) 28.In other words, each dilution gas supply unit 20 is associated with atleast one methane gas sensor 32, and control unit 24 is configured tocontrol dilution gas valve 28 of each dilution gas supply unit 20 basedon a signal received from associated methane gas sensor 32. Associationbetween methane gas sensor 32 and dilution gas valve 28 may be based ona minimum distance between both.

For example, the dilution gas may be ambient air drawn from the surface,and/or methane gas-free regions of the underground. In the activatedstate of dilution gas supply units 20, dilution gas source 27 may ensurepresence of dilution gas in a pressurised state in dilution gas line 26,for example, in a pressure range between 5 bar and 6 bar.

Supply of dilution gas may be stopped if a methane gas concentration ofthe respective region, which is measured by a respective methane gassensor 32, returns to a value that is lower than a preset safetyconcentration threshold value.

In some embodiments, in addition to mine ventilation along arrows V,dilution gas from at least one of the plurality of dilution gas supplyunits 20 may be provided before, to, and/or behind the cutting regionrelative to a moving direction of a cutting region around reciprocatingextraction machine. For example, high methane gas concentrationsgenerated during cutting may be reduced due to preliminary measures(dilution before cutting region), direct measures (dilution of cuttingregion), and subsequent measures (dilution behind cutting region). Notethat, for providing dilution gas from dilution gas supply units 20before, to, and/or behind the cutting region, no measurements of methanegas concentrations are necessary.

Alternatively or additionally, control unit 24 may react on measuredmethane gas concentrations in that a cutting speed of extraction machine10, a cutting depth of extraction machine 10, and/or an advancing speedof shield supports 16, and/or a conveyor speed of face conveyor 4. Forexample, cutting speed, cutting depth, conveyor speed, and/or advancingspeed may be reduced if a methane gas concentration value is greaterthan a preset threshold value.

In some embodiments, control unit 24 may be configured to control a mineventilation (for example along arrows V in FIG. 1) within its useablerange to increase or decrease ventilation through roadways 12 and alonglongwall face 2 based on measured methane gas concentrations.

As described above, control unit 24 may be further configured to controladvancing of shield supports 16, which may facilitate control over theventilation cross section, which may be defined by the longwall face 2,the roof, shield support 16 and floor. The per se known sequencedadvancing of the shield supports 16 may be decelerated or stopped at orbefore regions where an increased methane gas concentration is measured,which may keep the ventilation cross section at that region as large aspossible to vent off methane gas.

Alternatively or additionally, control unit 24 may be connected to faceconveyor 4 to control operation thereof. Control of a speed of faceconveyor 4 may have the effect that a faster transportation of extractedmaterial on face conveyor 4 may reduce the amount of outflow ofcapillary-bound methane gas of already extracted material transported onface conveyor 4 adjacent to longwall face 2. Instead, capillary-boundmethane gas of already extracted material may then outflow in aconsiderable amount after pass-over to roadway conveyor 14.

Additionally, dilution gas supply units 20 may be assisted by a waterbased deduster system (not shown). The water based deduster system maybe connected to control unit 24, which may also control operation of thewater based deduster system based on signals received from methane gassensors 32. For example, a plurality of water nozzles may be provided atshield supports 16 along longwall face 2.

In some embodiments, dilution gas nozzle 30 may be integrated into anozzle unit (not shown) of a shield support, which also comprises awater spray nozzle of the aforementioned water-based deduster system.

Based on a chronological sequence of measured methane gas concentrationsin each region by a respective methane gas sensor 32, control unit 24may be further configured to determine a temporal development of amethane gas concentration at each region. Thereby, control unit 24 mayderive a methane gas concentration trend for each region. Control unit24 may further determine at least one region for which the methane gasconcentration trend is greater than a preset threshold trend, and, inaddition to mine ventilation, control unit 24 may provide the dilutiongas to those regions for which the methane gas concentration trend isgreater than the preset threshold trend.

As described above, in some embodiments, dilution gas nozzle 30 may bemounted to or integrated into shield support 16 or face conveyor segment5 in an adjustable manner such that a direction in which a nozzle outletof dilution gas nozzle 30 is directed may be adjusted by control unit24, for example, based on measured methane gas concentrations. Forexample, nozzle outlet of dilution gas nozzle 30 may be directed to theregion where an increased methane gas concentration is measured.Providing dilution gas nozzles 30 in an adjustable manner may furtherfacilitate decreasing overall quantity of dilution gas nozzles 30 alonglongwall face 2. The reason is that an adjustable dilution gas nozzle 30may be capable to provide dilution gas to a greater region compared to adilution gas nozzle 30, which is not adjustable.

In some embodiments, control unit 24 determines a methane gasconcentration profile of longwall face 2 based on signals received fromthe methane gas sensors 32. Based on the determined methane gasconcentration profile, a plurality of different operation scenarios oflongwall mine 1 may be determined by control unit 24. Those operationscenarios may relate to at least one of variation of cutting speed,cutting depth, conveyor speed, dilution gas supply, ventilation, andadvancing speed. For example, in the case one methane gas sensor 32 maymeasure an increasing methane gas concentration, a first operationscenario may include a reduced cutting speed, a second operationscenario may include a reduced cutting depth, a third operation scenariomay include activation of at least one neighboring dilution gas supplyunit 20, and a third operation scenario may be a combination of thefirst, second and third operation scenario. Those operation scenariosmay be output from control unit 24 to display device 36. There, thedifferent operation scenarios may be presented to a user. The user maychoose one of the proposed operation scenarios via user input device 34.Based on the user chosen operation scenario, control unit 24 then maycontrol longwall mine 1.

A plurality of preset dilution gas supply programs may be stored incontrol unit 24. Examples of dilution gas supply programs may be adilution gas curtain, sequential spraying, and hot spot spraying.Dilution gas curtain may refer to a program, in which at least twoneighboring dilution gas units 20 may be caused to supply dilution gas.Sequential spraying may refer to a program, in which at least twoneighboring dilution gas units are activated sequentially, and hot spotspraying may refer to a program, in which at least one dilution gas unitis caused to supply dilution gas. For example, based on measured methanegas concentrations measured by methane gas sensors 32, control unit 24may determine one of the plurality of preset dilution gas supplyprograms, and may control dilution gas supply units 20 based on thedetermined dilution gas supply program. Alternatively, control unit 24may determine a dilution gas supply program in accordance with a userinput.

Contrary to a conventional mine ventilation, dilution gas supply units20 are specifically designed to allow providing dilution gas to methanegas concentration peak regions for diluting methane gas. Moreover,dilution gas supply units 20 and mine ventilation may work hand in handby increasing the effects of each other. For example, diluted methanegas diluted by dilution gas supply units 20 may be vented away fromlongwall face 2 by mine ventilation (along arrows V in FIG. 1).

Methane gas concentration peaks may move (flow) along longwall face 2 indirection of mine ventilation V (along arrow V in FIG. 1). Control unit24 may monitor movement of a methane gas concentration peak as signalsreceived from methane gas sensors 32 may indicate the same. Control unit24 may be configured to control dilution gas supply by dilution gasnozzles 30 to “chase” moving gas concentration peaks and/or to carry outpre-measures before a moving methane gas concentration peak reaches aspecific region. Pre-measures may be supply of dilution gas to thatspecific region before the moving (flowing) methane gas concentrationpeak reaches said specific region.

Accordingly, methane gas concentration peaks are considerably reduced,which may increase operational hours of longwall mine 1 as well asproductivity and safety while ensuring working conditions for man andmachine as dilution gas is only supplied to specific predeterminedregions.

According to another aspect, a dilution gas supply unit 20 is configuredfor use in a longwall mine 1 with a longwall face 2. Dilution gas supplyunit 20 comprises a dilution gas line 26, a dilution gas valve 28installed in dilution gas line 26, and a dilution gas nozzle 30 fluidlyconnected to dilution gas line 26, and configured to be installed at aposition facing longwall face 2.

In some embodiments, the dilution gas nozzle 30 of dilution gas supplyunit 20 is configured to provide dilution gas in an adjustable directionand/or amount.

Although the preferred embodiments of this invention have been describedherein, improvements and modifications may be incorporated withoutdeparting from the scope of the following claims.

1. A longwall installation unit configured to form a longwallinstallation assembly together with a plurality of longwall installationunits of the same kind to extend along the longwall face in a longwallmine having a compressor device, the longwall installation unitcomprising: a dilution gas nozzle configured to be fluidly connected tothe compressor device.
 2. The longwall installation unit of claim 1,wherein the longwall installation unit is configured as a shieldsupport.
 3. The longwall installation unit of claim 2, wherein theshield support further comprises: a shield cap; and a shield canopyconnected to the shield cap, wherein the dilution gas nozzle is mountedto the shield canopy.
 4. The longwall installation unit of claim 1,wherein the longwall installation unit is configured as a face conveyorsegment.
 5. The longwall installation unit of claim 4, wherein the faceconveyor segment further comprises: a material transport strand; areturn travel strand connected to the material transport strand; and aspill plate mounted at one side of the face conveyor segmented, whereinthe dilution gas nozzle is mounted to the spill plate.
 6. The longwallinstallation unit of claim 1, wherein the dilution gas nozzle isconfigured to provide dilution gas in at least one of an adjustabledirection and an adjustable amount.
 7. A longwall installation assemblyconfigured to be installed along a longwall face in a longwall mine, thelongwall installation assembly comprising: a plurality of longwallinstallation units configured to be arranged along the longwall face,wherein each of a sub-group of the plurality longwall installation unitsincludes a respective dilution gas nozzle; a compressor device fluidlyconnected to the respective dilution gas nozzle to provide pressurizeddilution gas; and a control unit configured to control the dilution gasflow from the compressor device to the respective dilution gas nozzle.8. The longwall installation assembly of claim 7, further including: arespective dilution gas valve associated with the dilution gas nozzle,wherein the control unit is configured to control the dilution gas flowthrough the dilution gas nozzle by adjusting the respective dilution gasvalve.
 9. The longwall installation assembly of claim 7, furthercomprising: a plurality of methane gas sensors installed at spatiallyseparated positions along the longwall face, each methane gas sensorbeing connected to the control unit, wherein the control unit is furtherconfigured to control at least one of the respective dilution gas valveand the compressor device based on signals received from the methane gassensors.
 10. The longwall installation assembly of claim 9, wherein thecontrol unit is further configured to control, based on signals receivedfrom the methane gas sensors, at least one of a cutting speed of anextraction machine, a cutting depth of the extraction machine, anadvancing of a plurality of shield supports, and a conveyor speed of aface conveyor.
 11. The longwall installation assembly of claim 8,wherein the sub-group includes every second longwall unit.
 12. A methodfor ensuring working conditions along a longwall face in a longwallmine, the method comprising: providing a mine ventilation; and providinga dilution gas to the longwall face from at least one of a plurality ofdilution gas supply units arranged at spatially separated positionsalong the longwall face.
 13. The method of claim 12, further comprising:measuring a methane gas concentration at a plurality of spatiallyseparated regions along the longwall face; determining at least oneregion for which the methane gas concentration value is greater than apreset threshold value; and providing the dilution gas from at least oneof the plurality of dilution gas supply units to the at least one regionfor which the methane gas concentration value is greater than the presetthreshold value.
 14. The method of claim 12, further comprising: cuttingmaterial in a cutting region reciprocating along the longwall face; andproviding the dilution gas to at least one of a first region before acutting region, a second region corresponding to the cutting region, anda third region behind the cutting region relative to a moving directionof the cutting region.
 15. The method of claim 12, further comprising:spraying a liquid in the at least one region for which the methane gasconcentration value is greater than the preset threshold value; andreducing at least one of a cutting speed, a cutting depth, a conveyorspeed, and an advancing speed if a methane gas concentration value isgreater than a preset threshold value.
 16. The longwall installationunit of claim 1, further including a dilution gas valve fluidlyconnected to the dilution gas nozzle.
 17. The longwall installation unitof claim 2, wherein the shield support comprises: a shield cap; and ashield canopy connected to the shield cap, wherein the dilution gasnozzle is mounted to the shield cap.
 18. The longwall installationassembly of claim 9, wherein a spacing between adjacent methane gassensors ranges from 10 m to 30 m.
 19. The method of claim 12, furtherincluding: generating the dilution gas using a compressor device; anddirecting the dilution gas to the dilution gas supply units via aconduit connecting the compressor device and the dilution gas supplyunits.
 20. The method of claim 12, further including: selectivelyadjusting a dilution gas valve disposed between the compressor deviceand at least one dilution gas supply unit to control an amount ofdilution gas supplied by the at least one dilution gas supply unit.